1 /*
   2  * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/classLoaderDataGraph.hpp"
  27 #include "gc/g1/g1Analytics.hpp"
  28 #include "gc/g1/g1CollectedHeap.inline.hpp"
  29 #include "gc/g1/g1ConcurrentMark.inline.hpp"
  30 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  31 #include "gc/g1/g1MMUTracker.hpp"
  32 #include "gc/g1/g1Policy.hpp"
  33 #include "gc/g1/g1RemSet.hpp"
  34 #include "gc/g1/g1VMOperations.hpp"
  35 #include "gc/shared/concurrentGCPhaseManager.hpp"
  36 #include "gc/shared/gcId.hpp"
  37 #include "gc/shared/gcTrace.hpp"
  38 #include "gc/shared/gcTraceTime.inline.hpp"
  39 #include "gc/shared/suspendibleThreadSet.hpp"
  40 #include "logging/log.hpp"
  41 #include "memory/resourceArea.hpp"
  42 #include "runtime/handles.inline.hpp"
  43 #include "runtime/vmThread.hpp"
  44 #include "utilities/debug.hpp"
  45 
  46 // ======= Concurrent Mark Thread ========
  47 
  48 // Check order in EXPAND_CURRENT_PHASES
  49 STATIC_ASSERT(ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE <
  50               ConcurrentGCPhaseManager::IDLE_PHASE);
  51 
  52 #define EXPAND_CONCURRENT_PHASES(expander)                                 \
  53   expander(ANY, = ConcurrentGCPhaseManager::UNCONSTRAINED_PHASE, NULL)     \
  54   expander(IDLE, = ConcurrentGCPhaseManager::IDLE_PHASE, NULL)             \
  55   expander(CONCURRENT_CYCLE,, "Concurrent Cycle")                          \
  56   expander(CLEAR_CLAIMED_MARKS,, "Concurrent Clear Claimed Marks")         \
  57   expander(SCAN_ROOT_REGIONS,, "Concurrent Scan Root Regions")             \
  58   expander(CONCURRENT_MARK,, "Concurrent Mark")                            \
  59   expander(MARK_FROM_ROOTS,, "Concurrent Mark From Roots")                 \
  60   expander(PRECLEAN,, "Concurrent Preclean")                               \
  61   expander(BEFORE_REMARK,, NULL)                                           \
  62   expander(REMARK,, NULL)                                                  \
  63   expander(REBUILD_REMEMBERED_SETS,, "Concurrent Rebuild Remembered Sets") \
  64   expander(CLEANUP_FOR_NEXT_MARK,, "Concurrent Cleanup for Next Mark")     \
  65   /* */
  66 
  67 class G1ConcurrentPhase : public AllStatic {
  68 public:
  69   enum {
  70 #define CONCURRENT_PHASE_ENUM(tag, value, ignore_title) tag value,
  71     EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_ENUM)
  72 #undef CONCURRENT_PHASE_ENUM
  73     PHASE_ID_LIMIT
  74   };
  75 };
  76 
  77 G1ConcurrentMarkThread::G1ConcurrentMarkThread(G1ConcurrentMark* cm) :
  78   ConcurrentGCThread(),
  79   _vtime_start(0.0),
  80   _vtime_accum(0.0),
  81   _vtime_mark_accum(0.0),
  82   _cm(cm),
  83   _state(Idle),
  84   _phase_manager_stack() {
  85 
  86   set_name("G1 Main Marker");
  87   create_and_start();
  88 }
  89 
  90 class CMRemark : public VoidClosure {
  91   G1ConcurrentMark* _cm;
  92 public:
  93   CMRemark(G1ConcurrentMark* cm) : _cm(cm) {}
  94 
  95   void do_void(){
  96     _cm->remark();
  97   }
  98 };
  99 
 100 class CMCleanup : public VoidClosure {
 101   G1ConcurrentMark* _cm;
 102 public:
 103   CMCleanup(G1ConcurrentMark* cm) : _cm(cm) {}
 104 
 105   void do_void(){
 106     _cm->cleanup();
 107   }
 108 };
 109 
 110 double G1ConcurrentMarkThread::mmu_sleep_time(G1Policy* g1_policy, bool remark) {
 111   // There are 3 reasons to use SuspendibleThreadSetJoiner.
 112   // 1. To avoid concurrency problem.
 113   //    - G1MMUTracker::add_pause(), when_sec() and its variation(when_ms() etc..) can be called
 114   //      concurrently from ConcurrentMarkThread and VMThread.
 115   // 2. If currently a gc is running, but it has not yet updated the MMU,
 116   //    we will not forget to consider that pause in the MMU calculation.
 117   // 3. If currently a gc is running, ConcurrentMarkThread will wait it to be finished.
 118   //    And then sleep for predicted amount of time by delay_to_keep_mmu().
 119   SuspendibleThreadSetJoiner sts_join;
 120 
 121   const G1Analytics* analytics = g1_policy->analytics();
 122   double now = os::elapsedTime();
 123   double prediction_ms = remark ? analytics->predict_remark_time_ms()
 124                                 : analytics->predict_cleanup_time_ms();
 125   G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
 126   return mmu_tracker->when_ms(now, prediction_ms);
 127 }
 128 
 129 void G1ConcurrentMarkThread::delay_to_keep_mmu(G1Policy* g1_policy, bool remark) {
 130   if (g1_policy->use_adaptive_young_list_length()) {
 131     jlong sleep_time_ms = mmu_sleep_time(g1_policy, remark);
 132     if (!_cm->has_aborted() && sleep_time_ms > 0) {
 133       os::sleep(this, sleep_time_ms, false);
 134     }
 135   }
 136 }
 137 
 138 class G1ConcPhaseTimer : public GCTraceConcTimeImpl<LogLevel::Info, LOG_TAGS(gc, marking)> {
 139   G1ConcurrentMark* _cm;
 140 
 141  public:
 142   G1ConcPhaseTimer(G1ConcurrentMark* cm, const char* title) :
 143     GCTraceConcTimeImpl<LogLevel::Info,  LogTag::_gc, LogTag::_marking>(title),
 144     _cm(cm)
 145   {
 146     _cm->gc_timer_cm()->register_gc_concurrent_start(title);
 147   }
 148 
 149   ~G1ConcPhaseTimer() {
 150     _cm->gc_timer_cm()->register_gc_concurrent_end();
 151   }
 152 };
 153 
 154 static const char* const concurrent_phase_names[] = {
 155 #define CONCURRENT_PHASE_NAME(tag, ignore_value, ignore_title) XSTR(tag),
 156   EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_NAME)
 157 #undef CONCURRENT_PHASE_NAME
 158   NULL                          // terminator
 159 };
 160 // Verify dense enum assumption.  +1 for terminator.
 161 STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT + 1 ==
 162               ARRAY_SIZE(concurrent_phase_names));
 163 
 164 // Returns the phase number for name, or a negative value if unknown.
 165 static int lookup_concurrent_phase(const char* name) {
 166   const char* const* names = concurrent_phase_names;
 167   for (uint i = 0; names[i] != NULL; ++i) {
 168     if (strcmp(name, names[i]) == 0) {
 169       return static_cast<int>(i);
 170     }
 171   }
 172   return -1;
 173 }
 174 
 175 // The phase must be valid and must have a title.
 176 static const char* lookup_concurrent_phase_title(int phase) {
 177   static const char* const titles[] = {
 178 #define CONCURRENT_PHASE_TITLE(ignore_tag, ignore_value, title) title,
 179     EXPAND_CONCURRENT_PHASES(CONCURRENT_PHASE_TITLE)
 180 #undef CONCURRENT_PHASE_TITLE
 181   };
 182   // Verify dense enum assumption.
 183   STATIC_ASSERT(G1ConcurrentPhase::PHASE_ID_LIMIT == ARRAY_SIZE(titles));
 184 
 185   assert(0 <= phase, "precondition");
 186   assert((uint)phase < ARRAY_SIZE(titles), "precondition");
 187   const char* title = titles[phase];
 188   assert(title != NULL, "precondition");
 189   return title;
 190 }
 191 
 192 class G1ConcPhaseManager : public StackObj {
 193   G1ConcurrentMark* _cm;
 194   ConcurrentGCPhaseManager _manager;
 195 
 196 public:
 197   G1ConcPhaseManager(int phase, G1ConcurrentMarkThread* thread) :
 198     _cm(thread->cm()),
 199     _manager(phase, thread->phase_manager_stack())
 200   { }
 201 
 202   ~G1ConcPhaseManager() {
 203     // Deactivate the manager if marking aborted, to avoid blocking on
 204     // phase exit when the phase has been requested.
 205     if (_cm->has_aborted()) {
 206       _manager.deactivate();
 207     }
 208   }
 209 
 210   void set_phase(int phase, bool force) {
 211     _manager.set_phase(phase, force);
 212   }
 213 };
 214 
 215 // Combine phase management and timing into one convenient utility.
 216 class G1ConcPhase : public StackObj {
 217   G1ConcPhaseTimer _timer;
 218   G1ConcPhaseManager _manager;
 219 
 220 public:
 221   G1ConcPhase(int phase, G1ConcurrentMarkThread* thread) :
 222     _timer(thread->cm(), lookup_concurrent_phase_title(phase)),
 223     _manager(phase, thread)
 224   { }
 225 };
 226 
 227 bool G1ConcurrentMarkThread::request_concurrent_phase(const char* phase_name) {
 228   int phase = lookup_concurrent_phase(phase_name);
 229   if (phase < 0) return false;
 230 
 231   while (!ConcurrentGCPhaseManager::wait_for_phase(phase,
 232                                                    phase_manager_stack())) {
 233     assert(phase != G1ConcurrentPhase::ANY, "Wait for ANY phase must succeed");
 234     if ((phase != G1ConcurrentPhase::IDLE) && !during_cycle()) {
 235       // If idle and the goal is !idle, start a collection.
 236       G1CollectedHeap::heap()->collect(GCCause::_wb_conc_mark);
 237     }
 238   }
 239   return true;
 240 }
 241 
 242 void G1ConcurrentMarkThread::run_service() {
 243   _vtime_start = os::elapsedVTime();
 244 
 245   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 246   G1Policy* policy = g1h->policy();
 247 
 248   G1ConcPhaseManager cpmanager(G1ConcurrentPhase::IDLE, this);
 249 
 250   while (!should_terminate()) {
 251     // wait until started is set.
 252     sleep_before_next_cycle();
 253     if (should_terminate()) {
 254       break;
 255     }
 256 
 257     cpmanager.set_phase(G1ConcurrentPhase::CONCURRENT_CYCLE, false /* force */);
 258 
 259     GCIdMark gc_id_mark;
 260 
 261     _cm->concurrent_cycle_start();
 262 
 263     GCTraceConcTime(Info, gc) tt("Concurrent Cycle");
 264     {
 265       ResourceMark rm;
 266       HandleMark   hm;
 267       double cycle_start = os::elapsedVTime();
 268 
 269       {
 270         G1ConcPhase p(G1ConcurrentPhase::CLEAR_CLAIMED_MARKS, this);
 271         MutexLocker ml(ClassLoaderDataGraph_lock);
 272         ClassLoaderDataGraph::clear_claimed_marks();
 273       }
 274 
 275       // We have to ensure that we finish scanning the root regions
 276       // before the next GC takes place. To ensure this we have to
 277       // make sure that we do not join the STS until the root regions
 278       // have been scanned. If we did then it's possible that a
 279       // subsequent GC could block us from joining the STS and proceed
 280       // without the root regions have been scanned which would be a
 281       // correctness issue.
 282 
 283       {
 284         G1ConcPhase p(G1ConcurrentPhase::SCAN_ROOT_REGIONS, this);
 285         _cm->scan_root_regions();
 286       }
 287 
 288       // It would be nice to use the G1ConcPhase class here but
 289       // the "end" logging is inside the loop and not at the end of
 290       // a scope. Also, the timer doesn't support nesting.
 291       // Mimicking the same log output instead.
 292       {
 293         G1ConcPhaseManager mark_manager(G1ConcurrentPhase::CONCURRENT_MARK, this);
 294         jlong mark_start = os::elapsed_counter();
 295         const char* cm_title = lookup_concurrent_phase_title(G1ConcurrentPhase::CONCURRENT_MARK);
 296         log_info(gc, marking)("%s (%.3fs)",
 297                               cm_title,
 298                               TimeHelper::counter_to_seconds(mark_start));
 299         for (uint iter = 1; !_cm->has_aborted(); ++iter) {
 300           // Concurrent marking.
 301           {
 302             G1ConcPhase p(G1ConcurrentPhase::MARK_FROM_ROOTS, this);
 303             _cm->mark_from_roots();
 304           }
 305           if (_cm->has_aborted()) {
 306             break;
 307           }
 308 
 309           if (G1UseReferencePrecleaning) {
 310             G1ConcPhase p(G1ConcurrentPhase::PRECLEAN, this);
 311             _cm->preclean();
 312           }
 313 
 314           // Provide a control point before remark.
 315           {
 316             G1ConcPhaseManager p(G1ConcurrentPhase::BEFORE_REMARK, this);
 317           }
 318           if (_cm->has_aborted()) {
 319             break;
 320           }
 321 
 322           // Delay remark pause for MMU.
 323           double mark_end_time = os::elapsedVTime();
 324           jlong mark_end = os::elapsed_counter();
 325           _vtime_mark_accum += (mark_end_time - cycle_start);
 326           delay_to_keep_mmu(policy, true /* remark */);
 327           if (_cm->has_aborted()) {
 328             break;
 329           }
 330 
 331           // Pause Remark.
 332           log_info(gc, marking)("%s (%.3fs, %.3fs) %.3fms",
 333                                 cm_title,
 334                                 TimeHelper::counter_to_seconds(mark_start),
 335                                 TimeHelper::counter_to_seconds(mark_end),
 336                                 TimeHelper::counter_to_millis(mark_end - mark_start));
 337           mark_manager.set_phase(G1ConcurrentPhase::REMARK, false);
 338           CMRemark cl(_cm);
 339           VM_G1Concurrent op(&cl, "Pause Remark");
 340           VMThread::execute(&op);
 341           if (_cm->has_aborted()) {
 342             break;
 343           } else if (!_cm->restart_for_overflow()) {
 344             break;              // Exit loop if no restart requested.
 345           } else {
 346             // Loop to restart for overflow.
 347             mark_manager.set_phase(G1ConcurrentPhase::CONCURRENT_MARK, false);
 348             log_info(gc, marking)("%s Restart for Mark Stack Overflow (iteration #%u)",
 349                                   cm_title, iter);
 350           }
 351         }
 352       }
 353 
 354       if (!_cm->has_aborted()) {
 355         G1ConcPhase p(G1ConcurrentPhase::REBUILD_REMEMBERED_SETS, this);
 356         _cm->rebuild_rem_set_concurrently();
 357       }
 358 
 359       double end_time = os::elapsedVTime();
 360       // Update the total virtual time before doing this, since it will try
 361       // to measure it to get the vtime for this marking.
 362       _vtime_accum = (end_time - _vtime_start);
 363 
 364       if (!_cm->has_aborted()) {
 365         delay_to_keep_mmu(policy, false /* cleanup */);
 366       }
 367 
 368       if (!_cm->has_aborted()) {
 369         CMCleanup cl_cl(_cm);
 370         VM_G1Concurrent op(&cl_cl, "Pause Cleanup");
 371         VMThread::execute(&op);
 372       }
 373 
 374       // We now want to allow clearing of the marking bitmap to be
 375       // suspended by a collection pause.
 376       // We may have aborted just before the remark. Do not bother clearing the
 377       // bitmap then, as it has been done during mark abort.
 378       if (!_cm->has_aborted()) {
 379         G1ConcPhase p(G1ConcurrentPhase::CLEANUP_FOR_NEXT_MARK, this);
 380         _cm->cleanup_for_next_mark();
 381       }
 382     }
 383 
 384     // Update the number of full collections that have been
 385     // completed. This will also notify the FullGCCount_lock in case a
 386     // Java thread is waiting for a full GC to happen (e.g., it
 387     // called System.gc() with +ExplicitGCInvokesConcurrent).
 388     {
 389       SuspendibleThreadSetJoiner sts_join;
 390       g1h->increment_old_marking_cycles_completed(true /* concurrent */);
 391 
 392       _cm->concurrent_cycle_end();
 393     }
 394 
 395     cpmanager.set_phase(G1ConcurrentPhase::IDLE, _cm->has_aborted() /* force */);
 396   }
 397   _cm->root_regions()->cancel_scan();
 398 }
 399 
 400 void G1ConcurrentMarkThread::stop_service() {
 401   MutexLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
 402   CGC_lock->notify_all();
 403 }
 404 
 405 
 406 void G1ConcurrentMarkThread::sleep_before_next_cycle() {
 407   // We join here because we don't want to do the "shouldConcurrentMark()"
 408   // below while the world is otherwise stopped.
 409   assert(!in_progress(), "should have been cleared");
 410 
 411   MonitorLocker ml(CGC_lock, Mutex::_no_safepoint_check_flag);
 412   while (!started() && !should_terminate()) {
 413     ml.wait();
 414   }
 415 
 416   if (started()) {
 417     set_in_progress();
 418   }
 419 }